Synthesis and rearrangements of 1,2,2,4,4,-Pentamethylbicyclo[1,1,0]butane

Abstract

The synthesis of the title compound (3) by the intramolecular displacement of alkoxide ion is reported. Acid-catalysed rearrangement of (3) gave 2,3,5-trimethylhexa-l,4-diene (9), 2,3,5-tri- methylhexa-2,4-diene (10) and 2,4,5-trimethylhexa-1,4-diene (11) in the ratio of c. 3 : 3 : 7 respectively. Pyrolytic rearrangement of (3), in the vapour phase in the presence of triethylamine, gave the same products but the ratio of (9) to (11) was 3 : 1. This change in the ratio of (9) : (11) is consistent with an initial non-concerted cleavage of the bicyclobutane to give diradical species.